A collection of proofs in the PR format. The origin of the proofs is listed below
Marijn J.H. Heule, Benjamin Kiesl, and Armin Biere (2017). Short Proofs Without New Variables. In Automated Deduction - CADE-26, pp. 130-147. Lecture Notes in Computer Science 10395, Springer.
Marijn J. H. Heule and Armin Biere (2018). What a Difference a Variable Makes. In Tools and Algorithms for the Construction and Analysis of Systems - TACAS 2018, pp. 75-92. Lecture Notes in Computer Science 10806, Springer.
Marijn J. H. Heule, Benjamin Kiesl, and Armin Biere (2019). Clausal Proofs of Mutilated Chessboards. In NASA Formal Methods (NFM), pp. 204-210. Lecture Notes in Computer Science 11460, Springer.
Emre Yolcu, Xinyu Wu, and Marijn J. H. Heule (2020). Mycielski graphs and PR proofs. In Theory and Practice of Satisfiability Testing - SAT 2020, pp. 201-217. Lecture Notes in Computer Science 12178, Spinger.